Paul Hammant's Blog:
Push or pull of config changes for a production stack

So Logan has a viable “Application Configuration Application” (ACA). I’m reminded that I should never be allowed to name things. Hot Toggles (TM) might have been a better name for the thing. It’s reallyworthchecking out.

An outstanding issue is how to get changed config data (JSON) to the nodes in a production stack that need it. We’ve implemented one simple mechanism for a sample Java app. In time we’d need to have code snippets (or reusable libraries) for many regular enterprise language choices.

Here’s a brain-dump of the choices, without mentioning specific languages:

Where configurable nodes access ACA (pull)

Polling for changes on a separate thread

might suffer from thread death, and have restart issues

threads might be idiomatically incorrect for ‘container’

not all languages allow thread spawning

Polling for changes associated with a end-user request

blocking issues?

Could happen ahead of serving of request

Could happen after the response is served

For this design to work, the configurable nodes would need authentication details for the ACA

Where ACA directly modifies configurable nodes (push)

ACA directly pushes changed config to the nodes

ACA needs to authenticate with nodes, which feels backwards

multi-threading may help shorten the delay in updating many nodes

ACA has to maintain a list of the nodes that need updates

ACA pushes changed config on to a message bus, to which the nodes subscribe

encryption of data on the bus could be important

Hmm, I wonder if there is a Memcache/Ehcache way of securely percolating changed config…